Many systems are available to provide for the spreading of material, such as sand, salt, gravel, asphalt and the like, onto a surface. By way of example only, a conventional dump or V-box vehicle can include a conveyor system that transports material residing within a body of the vehicle out of the body and into one or more spreaders mounted on the exterior of the vehicle. Such conveyor systems typically include a longitudinal screw or endless conveyor located within the body that transports the material from the front to the rear of the body. A conventional spreader is mounted on the rear of the vehicle to receive the material for discharge onto the roadway.
Today, municipalities dispense granular materials on roadways during slick winter conditions to improve traction for vehicles driving in those conditions. Salt is sometimes used to melt snow and ice, while other materials, such as sand, for example, can be used to improve traction. Significant direct costs are incurred in this process, including the costs for the materials themselves as well as equipment and labor costs involved in the application of the materials. Time is also spent traveling to and from the stockpiles of material and back to the various routes throughout the region.
The placement process of such material on roadways has historically involved two methods. The first method utilizes a rotating “spinner disc,” as will be known to those of skill in the art. In this process, metered amounts of granular material are dropped onto the spinning disc, which spins about a vertical axis. The disc includes a plurality of ridges or vanes oriented in a generally spoke-like arrangement. As the disc rotates, material is thrown in a pattern onto the roadway. A slow turning disc distributes the material in a relatively narrow pattern approximately a few feet in width. Higher rotational speeds can create spread width patterns of forty feet or more. A series of baffles and diverters placed around the disc can aid in narrowing the pattern to produce a more desirable spread pattern. However, such baffles and diverters provide only limited control over material placement.
The second common method for spreading materials on roadways is to drop the material directly onto the road surface in either a narrow strip or metered across a much wider path, approximately six to seven feet. The narrow strip is accomplished by discharging the material through a single opening, while a wider path can be created using a “roll type” spreader. However, both of these methods involve dropping material straight down onto the roadway (i.e. with no pattern control of the particles).
Both of these methods can result in efficiency problems. For example, application rates are usually increased to compensate for losing the material to non-roadway surfaces. Accordingly, material costs increase as a result of spreading material on areas where it is not needed. Fuel costs increase as many more trips are spent to and from the material stockpiles to replenish the material spread upon the roadways. More equipment and operators are needed to cover the roads within the same time period because of this increase in lost time traveling to stockpiles.
In recent years, the practice of adding liquid to salt to aid in the melting of snow and ice has become more common. Brine (salt water) and other liquids are frequently added to the salt (sometimes referred to as “pre-wetting”), and the chemical reactions of melting snow are more quickly activated. Advantages of this wetter material (in addition to causing the salt to act faster) include: providing a stickier material that adheres to the road better; reducing the bounce of material to areas outside the targeted zone to allow for further reductions in salt application rates which extend truck routes; and reducing refill trips and the number of vehicles needed to support a municipality. Units which dispense this wetter material mix are currently available from multiple commercial sources. However, such units have relatively high capital costs and can be difficult to operate and maintain due to their complexity.
In view of the foregoing, there exist various needs in the art. One such need is for a spreader that helps control the dispensing of particles to permit selective application of particulate material to a roadway in a predetermined pattern relative to the vehicle travel path. Another need is for a spreader system that allows an operator to readily adjust the character of the dispensing pattern.